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Biomedical subjects

W C Davis

Publications and source records attributed to W C Davis.

At least 253 records · Page 14Linked to original sources
PubMed1978

Synthesis of DNA and protein by Anaplasma marginale in bovine erythrocytes during short-term culture.

Bovine erythrocytes infected with Anaplasma marginale were cultured for 1 to 5 days in a CO2 incubation chamber, pulse-labeled with [3H]thymidine and [14C]methionine, lysed, and fractionated by differential centrifugation and continuous density gradient centrifugation in Renografin. Anaplasma and associated fragments of stroma formed two distinct bands in the dense region of the gradient. Electron microscopic examination of pelleted material from the bands from cells cultured for 1 day revealed the presence of organisms that were morphologically intact or in various states of degeneration. Examination of fractions from the gradient for incorporation of label revealed that analplasma present in erythrocytes can incorporate both [3H]thymidine and [14C]methionine. Subsequent experiments demonstrated that organisms cultured for 3 and 5 days incorporated the radiolabeled compounds also, but to a lesser extent. The experiments demonstrate that it is possible to culture analplasma in vitro for short periods of time and monitor their growth characteristics.

Anaplasma↗
PubMed1978

Evaluation of reconstitution of immunodeficient mice by partially purified thymic extracts.

Partially purified thymus products were used to evaluate the maturation of T lymphocytes in immunodeficient mice. Three different bovine thymic extracts, designated thymic extracts A, B, and C, were successful in increasing the longevity of conventionally raised nude mice. Daily injection of bovine thymic extracts A, B, and C and mouse thymus extracts failed to mature a population of T lymphocytes and restore the capacity to reject heart allografts. Preincubation of normal syngeneic bone marrow with thymic extract B in vitro before injection into nude mice also failed to reconstitute the host's ability to reject heart grafts. The number of antibody plaque-forming cells of sheep red blood cells in lethally irradiated, bone marrow-reconstituted mice could be increased by preincubating the bone marrow cells with bovine thymic extract fraction B before injection followed by daily injections. A similar but less marked increase in plaque-forming cells was obtained by the daily injection of bovine thymic extract fraction C. Complete functional maturation of T lymphocytes in immunodeficient animals appears to require more than thymic extract stimulation of bone marrow cells or pre-T lymphocytes.

Animals↗
PubMed1978

Regulation by antibody of lectin-induced lymphocyte proliferation: antibody inhibition of mitogenesis and release of lectin from cell surfaces.

Studies were conducted to determine the ways in which antibody regulates proliferation of lymphocytes stimulated by phytohemagglutinin (PHA) and concanavalin A (ConA). Equine lymphocytes were reacted with PHA or ConA for 1 to 10 hours, washed free of excess lectin, then cultured for 3 days and examined for proliferation and incorporation of [3H]thymidine. Both PHA and ConA induced lymphocytes to proliferate after short incubation periods. This response could be interrupted by the addition of antibody to the respective lectin. Total suppression of the proliferative response occurred if antibody was added within the first 2 hours after initial contact with PHA or ConA. Addition at times up to 48 hours produced either total or partial suppression. The removal of excess antibody 4 hours after addition to the culture did not reverse the suppression. Using radiolabeled ConA and PHA, it was observed that suppressive antibody inhibited the release of lectin from metabolically active lymphocytes and from surfaces where pinocytosis was not possible or was minimized. Antibody did not affect the rate of degradation of lectin by the cells. These results indicate that antibody attached to lectins, already bound to the lymphocyte surface, can terminate the lymphocyte response and retard the rate of release of lectin from the cell membrane.

Antibodies↗
PubMed1977

Evaluation of free-roaming mule deer as carriers of anaplasmosis in an area of Idaho where bovine anaplasmosis is enzootic.

Samples of blood from 87 Rocky Mountain mule deer (Odocoileus hemionus hemionus) were inoculated into 3 susceptible splenectomized calves to determine the anaplasmosis carrier status of the deer. The deer were trapped along the Idaho-Utah state boundary, near Stone, Id. Acute anaplasmosis was induced in 2 of the 3 inoculated calves, and blood from the 3 calves caused anaplasmosis when inoculated into adult non-splenectomized cattle. Serum rapid card agglutination testing revealed 13 (14.9%) positive reactions among the 87 mule deer. When these seropositive samples were evaluated with the complement-fixation test, positive reactions were not found and only 3 (3.5%) serums gave suspect reactions. A serologic survey for anaplasmosis in 1,852 cattle that cohabit spring and summer rangeland areas with mule deer revealed 14.5% reactors by the serum rapid card agglutination test. The study area consisted of an ecosystem that supports cattle, free-roaming mule deer, and Dermacentor andersoni, and thus contained the elements necessary to effect interspecies transmission of Anaplasma marginale. The significance of wildlife reservoirs and their bearing on anaplasmosis control and eradication programs needs further investigation.

Anaplasmosis↗
PubMed1977

Effect of length of treatment with Bayer 2502 on isolation of Trypanosoma cruzi and resistance to challenge in the mouse.

The effect of length of treatment of Trypanosoma cruzi with Bayer 2502 (Bay 2502, Lampit, Nifurtimox) on resistance to challenge and parasite isolation was studied in two experiments. In each, 200 mice were divided into groups of 20, infected with T. cruzi, and then treated with Bay 2502 for 1 to 8 consecutive weeks. Sixteen weeks after exposure, 10 mice from each experimental group were challenged with 150,000 trypomastigotes. The remainder were maintaned for 8 more weeks and killed for isolation of parasites. Mice treated with Bay 2502 for up to 8 consecutive weeks were uniformly resistant to challenge, and parasites could not be isolated from groups treatef for over 6 weeks. Results suggest that prolonged treatment with Bay 2502 eliminates T. cruzi from infected hosts and that resistance to challenge is not dependent on the presence of the organisms in mice.

Animals↗
PubMed1977

The Chediak-Higashi syndrome of cats.

Initial clinical, genetic, cytochemical and ultrastructural studies have characterized the Chediak-Higashi syndrome in cats. Three cats with Chediak-Higashi syndrome were found in a single line of 27 Persian cats, and three additional affected cats were produced from two prospective breedings of the original line. The disorder was characterized genetically as an autosomal recessive condition. All cats in the line with the combination of yellow eye color and "blue smoke" hair color exhibited the disorder. Four of the five cats examined had bilateral nuclear cataracts as early in life as 3 months of age. No increased susceptibility to infectious disease was observed. A bleeding tendency was noted. Abnormally large eosinophilic, sudanophilic, peroxidase-containing granules were observed in the neutrophils of the granulocytic series of blood and bone marrow by electron and light microscopy. Granules of eosinophils and basophils were also enlarged. Light microscopic studies of hair and skin revealed enlarged melanin granules. These manifestations were similar to those in man, mink, cattle, mice, and the killer whale with Chediak-Higashi syndrome. Cats are the sixth species in which this genetic disease has been reported.

Animals↗
PubMed1976

Distribution of transplantation antigens on cell surfaces.

Significant advances have been made over the past few years in elucidating the genetics, the chemical composition, and, more recently, the in situ relation of the major histocompatibility antigens of the mouse and man. Attempts to map the arrangement of individual antigens on the surface of cells have revealed that some antigens specified by a given subregion of both the H-2 and HL-A systems are in close proximity on the cell membrane and that attachment of antibody to one site to a certain degree blocks or inhibits the binding of antibody to the adjacent site. Allelic antigens in the H-2 system tend to inhibit binding. H-2D and H-2K antigens show either inhibition or noninteraction, possibly reflecting a cis-trans effect. Unlike with the H-2, inhibition of binding occurs only between HL-A antigens specified by homologous chromosomes. Also, a number of instances have been noted where inhibition of binding is unidirectional, possibly reflecting a polymeric nature of antigen or stratification of moieties at cell surface. Inhibition of antibody attachment between several alloantigenic systems on thymocytes in mice and also a variation in the mobility of the histocompatibility antigens suggest that the moieties bearing histocompatibility antigens are comprised of several gene products. Further work is needed to establish the validity of this assumption and to fully define the composition of these units. Ample data have been obtained from both biological and biophysical experiments to support the suggestion that single or multiple complexes of glycoproteins can move in the plane of the membrane. Although the composition of these cell membrane components remains a question, direct visualization by fluorescence and electron microscopy indicates that these moieties are small and, under natural conditions, distributed uniformly over the cell surface. Direct and indirect labeling techniques have shown that the complexes have no fixed position in the cell membrane and can be displaced laterally in the plane of the membrane without affecting the distribution of other surface molecules, such as sIg and species-specific antigens. Additional evidence suggests that H-2D and H-2K antigen complexes, as well as their gene products specified by different parent chromosomes, may be displaced separately. These observations are especially interesting and must be reconciled and data obtained by proximity analysis which indicate an association of some allelic products and possibly certain combinations of D and K antigens. Whether the differences noted in reactivity of the various surface antigens following attachment of antibodies are attributable to difference in size or to differences in the manner of their intercalation in the cell membrane remains to be elucidated. The rapid advances in elucidation of the molecular structure of biological membranes suggest that experimental work should be done on the biophysics of the structure of the antigenic sites and the mechanism of migration...

Animals↗
PubMed1976

Synthesis of immunoglobulin and Marek's disease virus antibody in susceptible and relatively resistant chickens.

The levels of IgM, IgY, and IgA and the development of specific antibody to Marek's disease virus (MDV) and sheep red blood cells (SRBC) in young chickens susceptible and resistant to Marek's disease were compared after exposure to MDV. No significant difference was noted in the immunoglobulin levels. However, the antibody response to MDV and SRBC occurred more rapidly in susceptible birds. The initial titer of antibody to these antigens was higher. These differences in response, however, were transient. At 3 weeks post exposure, the levels of IgM antibodies to MDV and antibodies to SRBC were similar in the two lines of chickens. At 6 weeks, the levels of IgY antibodies to MDV and antibodies detected by the agar gel precipitation test were similar.

Animals↗
PubMed1976

The effect of heat-killed streptococci on the survival of heart grafts in inbred strains of mice.

Studies with inbred strains of mice revealed that exposure to type 12, Group A, beta-hemolytic streptococci affects the host response to heart grafts implanted in the ear. Intraperitoneal injection of streptococci 10 days before grafting led to curtailed survival of syngrafts without altering the normal rejection time of allografts. Similar sensitization, combined with local injection of streptococci into the graft site at the time of grafting, was followed by rapid rejection of both syngrafts and allografts. The time interval between exposure and grafting was critical. Injection with streptococci 5 days before grafting led to a prolonged survival of allografts and no demonstrable effect on syngrafts. In contrast, injection of streptococci 15 days before grafting did not alter survival of either type of graft. The data indicate heart grafts implanted in the ear may serve as a useful model for the study of the host responses to streptococcal antigens.

Animals↗
PubMed1976

Reconstruction of defects of the mandible.

A series of 14 mandibular reconstruction in 13 patients with chips of autogenous, cancellous bone and marrow supported by a titanium mesh tray is presented. The mandibular defects were the results either of operation for carcinoma of the tongue and the floor of the mouth or trauma. Satisfactory rehabilitation was accomplished in 11 patients. The advantages of this technique are ease of accomplishment, ability to replace long and awkardly shaped segments, less shrinkage due to bone resorption, and shorter intermaxillary fixation.

Adult↗
PubMed1976

Alterations of the thymus and other lymphoid tissue in young horses with combined immunodeficiency.

Combined immunodeficiency (CID) is a significant disease in terms of prevalence in Arabian foals and is a useful animal for study of a similar condition in children. Thymuses from all CID foals examined were extremely hypoplastic. Light and electron microscopic examination of thymuses from CID foals, as well as a thymus from an aborted CID fetus, demonstrate that the basic thymic structure is intact, despite a number of dissimilar morphologic appearances. From these data, we inferred that the thymic hypoplasia was caused by a failure of committed lymphocytes from the bone marrow to populate the organ. The lack of uniform organized lymphocytes in the spleen and lymph nodes provides considerable support for the absence of lymphoid precursors or their inability to respond to differentiating influences.

Animals↗
PubMed1975

Canine granulocytopathy syndrome: neutrophil dysfunction in a dog with recurrent infections.

A male Irish Setter dog had a clinical history of recurrent life-threatening bacterial infections, with associated periods of pyrexia and severe neutrophilia. Examination of a mandibular lymph node biopsy made when the patient was 10 weeks old revealed subacute diffuse suppurative lymphadenitis with reticuloendothelial hyperplasia. Circulating leukocytes isolated from the dog when it was 5 months old had a marked bactericidal defect when compared with cells from clinically normal dogs of the same age. The clinical syndrome in the affected patient resembled that observed in the granulocytopathies described in man and other animals.

Animals↗